Background table headers overlaps border-radius

Description

Well, I found a very minor glitch in the admin UI
The "table.widefat" has rounded corners and the headers of that table have a gradient background, the problem is however that in all major browsers the background overlaps the border-radius, see the attached image.
I understand that this is VERY minor (5 pixels maybe?) but hey, if there is something to fix we should fix it
Tested in Chrome 6.0.490.1 dev and Firefox 3.6.6
Patch is included